Micro-electromechanical RF/microwave components, such as switches, phase shifters, and passive elements, have been demonstrated to have high performance, low cost, inherently smaller size, and low power consumption. These components include micro-cantilevers and micro-bridges. These components can also be used as sensors by doping or sensitizing a portion of the tip or body of the micro-cantilever, as a tool for DNA replication, as a tool for conductivity measurements, and as probes for multiple uses. For a micro-cantilever to be useful as an actuator such as in an RF switch, the actuation voltage of the micro-cantilever should be as low as possible to be compatible with the voltage sources integrated or combined with the RF circuit in which the switch is used such that additional high voltage sources are avoided.
The pull-in voltage (i.e., actuation voltage) of a simple micro-cantilever as a function of its dimensions and material properties is                               V          P1                =                                            2              ⁢                              Ed                0                3                            ⁢                              t                3                                                    27              ⁢                              ɛ                0                            ⁢                              L                4                                                                        (        1        )            where E is the Young's modulus, d0 is the initial gap between the micro-cantilever and the actuation electrode, t is the thickness, L is the length of the cantilever, and ε0 is the permittivity of the air.
From equation 1, it can be seen that the design parameters for a specific pull-in voltage are the dimensions of the micro-cantilever. For a given manufacturing technology where material properties and the initial gap do and thickness t are usually fixed, the only design parameter is the length of a cantilever. In order to lower the actuation voltage, one is forced to use long cantilevers as illustrated in FIG. 13 that require a tight control over the stress and stress gradient along the length. The long lengths require a critical point drying process to avoid stiction during the manufacturing process. Stiction occurs when surfaces are pulled together by capillary force when the wet etchant between two layers dries out. Stiction results in the moving portions of the cantilever structure being stuck to the non-moving (e.g., stationary) portions of the cantilever structure.
What is needed, therefore, is a high performance, low cost, low-pull-in voltage micro-cantilever device.
The invention provides such a device. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.